I typically grow 6-8 tomato plants.

One of my absolute favorites for canning is called Amish Paste. WAY better than standard Roma. Bigger, more productive, thicker flesh. If you want to can tomatoes, that's one you want to try. It's not uncommon to get Amish Paste tomatoes that are 12+ oz each, and tons of them. Only need a half dozen of them or so to make an entire batch of salsa. (My batches are 6-7 pints). That's how big they run, basically one tomato makes a pint jar of salsa.